Magnetic anisotropy of NaxCoO2 single crystals

Abstract

We report the magnetic properties of single crystals of Nax Co O2 (x=0.42, 0.82, and 0.87). The magnetic susceptibility measurements revealed considerable anisotropy along Hab and Hc for the as-grown single crystals. It was found that an antiferromagnetic transition with a Neel temperature TN =21 K occurred for the x=0.82 sample, and there was a paramagnetic phase for the x=0.87 sample over a wide temperature range from 2 to 300 K, but the sample with x=0.42 shows a monotonic increase of with increasing temperature above ∼100 K. In addition, the x=0.82 sample has the largest derived anisotropic g -factor ratio (gab gc ∼1.30), whereas the sample with x=0.42 is nearly isotropic (gab gc ∼0.96). © 2008 American Institute of Physics.